Muffler with resonance chambers for high and low frequencies



Sept. 24, 1968 w, POWERS ET AL 3,402,785.

MUFFLER WITH RESONANCE CHAMBERS FOR HIGH AND LOW FREQUENCIES 2 Sheets-Sheet 1 Filed Oct. 23, 1965 Walier HQO EZQ Haber? f7: f/cai'iz BY Sept. 24, 1968 w. H. POWERS ET AL 3,402,785

MUFFLER WITH RESONANCE CHAMBERS FOR HIGH AND LOW FREQUENCIES 2 Sheets-Sheet 2 Filed Oct. 23, 1965 Sr W R 1 M f a y 4 Z a yum W United States Patent 3,402,785 MUFFLER WITH RESONANCE CHAMBERS FOR HIGH AND LOW FREQUENCIES Walter H. Powers and Robert A. Heath, Jackson, Mich.,

assignors to Walker Manufacturing Company, a corporation of Delaware Filed Oct. 23, 1965, Ser. No. 503,692 12 Claims. (Cl. 181-48) ABSTRACT OF THE DISCLOSURE A closed. tuning tube, such as a Quincke tuner, is coupled to the gas stream through a spit chamber whereby the chamber volume and perforations act to broad band the attenuation range of the tuning tube.

This invention relates to a mufiler for the exhaust system of an internal combustion engine and more particularly to an improved low profile muffler.

The increased emphasis upon low silhouettes in modern motor vehicles has severely limited the space available beneath the vehicle in which to position the engine exhaust system. The demand for increased silence in modern vehicles has also placed an added burden upon the exhaust system design. Although it is a relatively simple matter to design an exhaust system that will attenuate most of the objectionable sound frequencies of the engine, the ideal system cannot be positioned beneath the modern motor vehicle due to its size.

It is, therefore, a principal object of this invention to provide an improved silencing device for an internal combustion engine that is compact in design.

It is a further object of this invention to provide a mufiler for the internal combustion engine of a motor vehicle that silences the most objectionable sounds of the exhaust system and yet may be conveniently positioned beneath the vehicle.

It is a further object of this invention to provide an improved mufiler for an internal combustion engine that achieves a degree of silencing heretofore thought impossible within the design requirements of modern vehicles.

A mufiler for an internal combustion engine embodying this invention comprises a tuning chamber defined by at least one shell. A plurality of perforations are provided in the shell opening into the tuning chamber whereby the tuning chamber functions as a spit chamber to attenuate high frequency sounds emanating from the engine. A quarter wave length tuning chamber is additionally provided that opens into the spit chamber.

Other objects and advantages of this invention will become more apparent as this description proceeds, particularly when considered in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a top plan view of a mufller for an internal combustion engine showing a first embodiment of this invention;

FIGURE 2 is an enlarged cross-sectional view of the mufller in FIGURE 1 taken in the plane of FIGURE 1;

FIGURE 3 is an enlarged cross-sectional view taken along the line 33 of FIGURE 1;

FIGURE 4 is an enlarged cross-sectional view taken along the line 44 of FIGURE 1;

FIGURE 5 is a cross-sectional view taken along the line 5-5 of FIGURE 1;

FIGURE 6 is a side elevational view showing another embodiment of the invention;

FIGURE 7 is a cross-sectional view taken along the line 7-7 of FIGURE 6;

FIGURE 8 is a side elevational view, in part similar to FIGURE 6, showing another embodiment of the invention; and

FIGURE 9 is a partial side elevational view, in part similar to FIGURES '6 and 8, showing still another embodiment of the invention.

Referring now in detail to the drawings and in particular to the embodiment shown in FIGURES 1 through 5, a muffler embodying this invention is identified generally by the reference numeral 11. The mufller 11 is adapted to be used in conjunction with the exhaust system of an internal combustion engine and is particularly adapted for use in motor vehicles wherein its low profile has optimum advantage, although the use is not so limited.

The muffier 11 is comprised of a tubular outer shell 12 that is necked down at one end, as at 13, to provide a bushing for attachment to another component of the engine exhaust system. The bushing 13 may be considered as the exhaust gas inlet bushing, although the mufiler could be reversed in the exhaust system, if so desired. The opposite end of the outer shell 12 is provided with a reduced diameter portion 14 which functions as a bushing for attachment to another component of the exhaust system and may be considered the exhaust gas outlet bushing.

A tubular inner shell 15 extends through the outer shell 12 coaxially with it and is received at each end thereof in the bushings 13 and 14. The inner shell 15 may be spotwelded as at 16 to the inlet bushing 13 and slidably received in the outlet bushing 14 to permit relative movement to compensate for differences in thermal expansion. Alternatively, the opposite end of the inner shell 15 may be affixed to the outlet bushing 14. In some other embodiments, both ends may be fixed to the bushings at the opposite ends of the outer shell 12.

The outer shell 12 is provided with a plurality of pinched down sections 17, 18, 19 and21 that engage the inner shell 15 around its circumference (FIGURE 3), to divide the space between the inner and outer shells into longitudinally spaced tuning chambers 22, 23, 24, 25 and 26. The inner shell 15 is provided with a plurality of longitudinally spaced louvered openings 27, 28, 29, 31 and 32 which open into the tuning chambers 22, 23, 24, 25 and 26, respectively, whereby the chambers 22 through 26 function as spit chambers to attenuate high frequency sounds emanating from the engine. The chambers 22 through 26 may be provided with different volumes or each may have the same volume.

The portion of the outer shell 12 which defines the outer periphery of the spit chamber 24 is provided with a flattened portion 33 that engages the inner shell 15 to provide clearance in this area for the under body of the vehicle. It should be readily apparent that the mufller thus far described is very compact in height. In a typical commercial embodiment, the outside diameter of the outer shell 12 maybe 3 inches or less.

The longitudinally spaced spit chambers 22, 23, 24, 25 and 26 are very effective in attenuating high frequency sounds emanating from the engine. Frequently, however, the engine will have one or more low frequency sounds which result in the generation of objectionable exhaust noises. Although a quarter wave length tuning chamber, commonly known as a Quincke tube, is effective in attenuating such low frequency noises, it was heretofore difficult to incorporate such a tuning device in the conventional mufiler.

The disclosed mufiier, however, effectively attenuates the most undesirable low frequency sound emanating from the engine and all harmonics of it by the provision of a side branch quarter length tuner, indicated generally by the reference numeral 34. The side branch tuner 34 is formed from a tubular member 35 that extends parallel to the longitudinal axes of the inner shell 15 and outer shell 12. An integral connecting neck 36 is provided at one end of the side branch tuner 34 which extends through an opening formed in the outer shell 12 and opening into the spit chamber 22. The opposite end of the quarter wave tuning chamber 34 is closed by a plug 37. This end of the tuning chamber is also supported by a bracket 38 that is welded to the outer shell 12 and the adjacent portion of the tubular member 35. The length of the quarter Wave length tuning chamber 34 is equal to one-quarter of the wave length of the objectionable frequency which is attenuated. As is well known, all odd harmonics of this frequency will also be silenced.

The connecting neck 36 may extend into any of the spit chambers and may open into either end of the outer shell 12 or any spaced location along it. It is most desirable, however, to position the opening of the quarter wave length tuning chamber 34 into the outer shell 12 at a point which coincides with an anti-node of the objectional frequency to be silenced. Preferably the area of the connecting neck and of the opening of the quarter wave length tuning chamber 34 into the outer shell 12 is the same as is the cross-sectional area along the length of the tubular member 35. The area of the opening into the spit chamber 22 is also considerably smaller than the volume of the spit chamber 22.

As is well known, the quarter wave length tuning chamber 34 is highly effective in silencing a given fre quency and all odd harmonics of the frequency. Normally, the location of such a device relative to an anti-node of the frequency to be silenced is critical. Since, however, the neck 36 connects the chamber 34 with the spit chamber 22, which has some volume and length, a broad banding effect is obtained that renders the location less critical. The provision of louvered openings between the tube 15 and the spit chamber which connects with the quarter wave length tuning device also has the effect of broad handing the device so that a wider range of frequencies may be accommodated or, alternatively, so that the location is not as critical.

It is well known to provide drain holes in the outer shells of mufflers so that condensate which forms within them may drain from the mufiler rather than accumulate within it. Such a drain hole (not shown), is provided in the outer shell 12. A drain hole 39 is also provided in the lower surface of the tubular member 35 so that condensate may drain from it.

The necessity for a separate drain hole in a side branch tuner may be eliminated by means of a construction of the type shown in FIGURE 6. In this embodiment, the construction of the outer shell 12 and the tuning mechanism provided by it is identical to that in the embodiment shown in FIGURES 1 through and will not be described again in detail. In this embodiment a quarter wave length side branch tuner, indicated generally by the reference numeral 51, and formed from an elongated tubular member 52 is provided with an inlet end that opens into one of the quarter wave length tuning chambers formed within the outer shell 12 of the muffler. The quarter wave length tuning chamber 51 also extends in substantially the same longitudinal direction as the outer shell 12 but its axis displaced or rotated upwardly from the horizontal about its opening into the outer shell 12 so that the tuning chamber slants downwardly toward the opening into the outer shell 12. This downward slant permits condensate which forms within the tuning chamber 51 to flow back into the outer shell 12 where it may be relieved from its drain hole (not shown).

The connection of the side branch tuner 51 to the outer shell 12 also differs somewhat in the embodiment of FIGURES 6 and 7 from that shown in FIGURES 1 through 5 as revealed by FIGURE 7. In this embodiment, the outer shell is formed with a flange or bushing 53 that receives an offset inlet neck 54 of the side branch tuner 51. The bushing 53 and inlet neck 54 may be spotwelded together at spaced locations around their circumference or, alternatively, a circumferential weld may be formed around their periphery.

As has been noted earlier, an object of this invention is the provision of a low profile tuning device. In the embodiment shown in FIGURES 1 through 5, the outer shell was formed with a flat central portion that provided for clearance of the muffler 11 beneath a motor vehicle. In some instances the location of the muflller makes it impossible to form it as a substantially straight unit. FIG- URE 8 illustrates such an embodiment and shows the application of a side branch tuner to said embodiment.

Referring now specifically to FIGURE 8, a muffler embodying this invention is identified generally by the reference numeral 61. The muffler 61 is comprised of an outer shell 62 that terminates at opposite ends in inlet and outlet bushings 63 and 64. Contained within the outer shell 62 in an inner shell (not shown) that is engaged around its periphery at spaced longitudinal locations by pinched down portions 65, 66, 67 and 68 of the outer shell 61. The pinched down portions 65 through 68 divide the space between the inner shell and outer shell 61 into a plurality of longitudinally spaced chambers and the inner shell is provided with a plurality of openings (not shown) into each of these chambers so that they will function as spit chambers, as in the previously described embodiment.

In this embodiment the outer shall 61 is comprised of two sections 69 and 71 that define longitudinal axes which are disposed at angle to each other and are interconnected by an arcuate portion 72. The inner shall is also formed in a like manner. The angular disposition of the sections 69 and 71 permits the muffler to be positioned adjacent an axle of the motor vehicle in which the muffier is used. The portion 71 of the outer shell 61 forms a so-called kick-up section that extends upwardly over the rear axle of the vehicle.

A quarter wave length side branch tuner, indicated generally by the reference numeral 73, is provided at one side of the mufller 61 and opens at one of its ends into one of the split chambers defined within the mufiler 61. The quarter wave length tuning device is comprised of first and second angularly related tubular sections 74 and 75 that are interconnected by an arcuate section 76. The sections 74, 75 and 76 correspond in disposition to the sections 69, 71 and 72, respectively, of the rnufller 61 so that even though the quarter wave length side branch tuner 73 is disposed alongside the mufiler -61 it is of substantially the same shape as the muffler 61.

In each of the previously described embodiments, the Side branch quarter wave length tuning device corresponded in shape to the outer shell of the muffler. The quarter wave length side branch tuner also extended for substantially the same length as the outer shell. In some instances, however, the required length of the quarter wave length tuner would be greater than the length of the outer shell or it might be impossible to have an appropriately long, straight side branch quarter wave length tuner.

FIGURE 9 illustrates an embodiment wherein the effective length can be extended without increasing the length of the device. In this embodiment a muffler embodying the invention is identified generally by the reference numeral 91. The muffier 91 will not be described in any detail other than to state that it may be considered to be of the same construction as the mufflers in the previously described embodiments and defines a plurality of spaced spit chambers. A quarter wave length tuning device, indicated generally by the reference numeral 92, is formed from a spiral shaped tubular member 93- having a closed outer end 94 and an inlet end 95 that is in communication with one of the spit chambers defined by the muffler 91. The spiral or snail shape of the shell 93 permits a greater effective length for a given longitudinal direction. It will be noted, however, that a somewhat greater height is required in this embodiment. This embodiment may be utilized in conjunction with vehicle constructions wherein the height at the desired location of the quarter wave length side branch tuner is relatively unimportant but where a length is required which cannot be accommodated in a straight direction beneath the vehicle.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope of fair meaning of the subjoined claims.

What is claimed is:

1. A mufiler for the exhaust system of an internal combustion engine comprising an inner shell, an outer shell positioned around said inner shell and defining a discrete tuning volume therebetween, a plurality of louvered openings in said inner shell for acoustic communication with said tuning volume, and a side branch tuner formed by a closed tube opening only at its other end through said outer shell into said tuning volume.

2. A mufller for the exhaust system of an internal combustion engine comprising an inner shell, an outer shell extending around said inner shell and engaging said inner shell at opposite end-s of said outer shell to define a tuning chamber with said inner shell, exhaust gas inlet means at one end of said inner shell and exhaust gas outlet means at the other end of said inner shell for straightthrough exhaust flow through said inner shell, a plurality of spaced perforations in said inner shell for exhaust gas communication between said inner shell and said tuning chamber whereby said tuning cham'ber functions as a spit chamber for attenuating high frequency sounds, and a closed quarter wave length tuning chamber opening at one end only into said spit chamber through said outer shell and tuned to attenuate a predetermined frequency.

3. A mufiier as set forth in claim 2 wherein the outer shell is provided with a plurality of reduced diameter portions along its length that engage the inner shell to divide the tuning chamber into a plurality of longitudinally spaced chambers, each of said chambers functioning as a spit chamber and the quarter wave length tuning chamber opening into only one of said spit chambers.

4. A mutfier as set forth in claim 3 wherein the perforations in the portion of the inner shell which open into the spit chamber that communicates with the quarter wave length tuning chamber are formed by louvered openings.

5. A mufiler for the exhaust system of an internal combustion engine comprising an inner shell, an outer shell positioned around said inner shell and engaging said inner shell at opposite ends of said outer shell to define a tuning chamber with said inner shell, exhaust gas inlet means at one end of said inner shell and exhaust gas outlet means at the other end of said inner shell for straight-through exhaust gas flow through said inner shell, a plurality of spaced perforations in said inner shell for exhaust gas communication between said inner shell and said tuning chamber whereby said tuning chamber functions as a spit chamber for attenuating high frequency sounds, a closed quarter wave length tuning chamber disposed alongside of said outer shell and extending in a substantially parallel direction with respect to said inner shell, said quarter wave length tuning chamber opening into said spit cham her through said outer shell, said quarter wave length tuning chamber being tuned to attenuate a pre-determined frequency.

6. A mufller for the exhaust system of an internal combustion engine as set forth in claim 5 wherein a drain hole is formed in the lower surface of the quarter wave length tuning device for draining condensate from said quarter wave length tuning device.

7. A mufiler for the exhaust system of an internal combustion engine as set forth in claim 5 wherein the quarter wave length tuning device is displaced upwardly a slight angle from the outer shell about its opening into the outer shell for draining condensate from said quarter wave length tuning device into said outer shell.

8. A mufiier for the exhaust system of an internal combustion engine comprising an inner shell, an outer shell positioned around said inner shell and engaging said inner shell at opposite ends of said outer shell to define a tuning chamber with said inner shell, exhaust gas inlet means at one end of said inner shell and exhust gas outlet means at the other end of said inner shell for straight-through exhaust gas flow through said inner shell, a mass of spaced perforations in said inner shell for exhaust gas communication between said inner shell and said tuning chamber whereby said truning chamber functions as a spit chamber for attenuating high frequency sounds, and a closed wall tube disposed alongside of said outer shell and extending in a substantially parallel direction with respect to said inner shell, means closing one end of said tube, the other end of said tube opening only into said spit chamber through said outer shell.

9. A muffler as set forth in claim 8 wherein the perforations in said inner shell are formed by louvered openings.

10. A mufiler for the exhaust system of an internal combustion engine comprising an inner shell, an outer shell positioned around said inner shell and engaging said inner shell at opposite ends of said outer shell to define a tuning chamber with said inner shell, exhaust gas inlet means at one end of said inner shell and exhaust gas outlet means at the other end of said inner shell for straight through exhaust gas flow through said inner shell, a plurality of spaced perforations in said inner shell for exhaust gas communication between said inner shell and said tuning chamber whereby said tuning chamber functions as a spit chamber for attenuating high frequency sounds, a quarter wave length tuning chamber disposed alongside of said outer shell, and a connection between said quarter wave length tuning chamber and said spit chamber through said outer shell, said quarter wave length tuning chamber being tuned to attenuate a predetermined frequency, said inner shell, said outer shell and said quarter wave length tuning chamber being comprised of two angularly related section-s and the respective sections of said shells and said quarter wave length tuning chamber being disposed in substantially parallel relationship to each other.

11. A mufiler for the exhaust system of an internal combustion engine comprising an inner shell, an outer shell positioned around said inner shell and engaging said inner shell at opposite ends of said outer shell to define a tuning chamber with said inner shell, exhaust gas inlet means at one end of said inner shell and exhaust gas outlet means at the other end of said inner shell for straight-through exhaust gas flow through said inner shell, a plurality of spaced perforations in said inner shell for exhaust gas communication between said inner shell and said tuning chamber whereby said tuning chamber functions as a spit chamber for attenuating high frequency sounds, a quarter wave length tuning chamber disposed alongside of said outer shell, said quarter wave length tuning chamber having a generally spiral shape, and a connection between said quarter wave length tuning chamber and said spit chamber through said outer shell, said spiral shaped quarter wave length tuning chamber having an effective length tuned to attenuate a predetermined frequency.

12. In an exhaust gas muflier for attenuating high frequencies and a predetermined low frequency, an outer shell having an inlet and an outlet for exhaust gases, a gas flow tube inside the shell and connecting the inlet and outlet to provide gas flow between the inlet and outlet, said gas flow tube having a mass of small perforations formed in the wall thereof, closed chamber forming means in the shell around said mass of perforations and acting with said perforations to form a spit chamber for attenuating high frequency sound in the gas, and a relatively long closed tube open only at one end and said one end opening only into said spit chamber so that the closed tube is coupled to gas flowing through said gas flow tube only through said spit chamber and said mass of perforations, said closed end tube being tuned to attenuate said predetermined low frequency.

References Cited UNITED 8 Moss.

Bourne 18148 Buck 18148 XR Gaugler. Sampoll et al. 18172 XR Ludlow et a1. 1- 18136 Walker 18161 XR FOREIGN PATENTS France.

(1st addition) Great Britain. Great Britain.

ROBERT S. WARD, JR., Primary Examiner. 

